diagnose-config

name	diagnose-config
description	Diagnose MegaLinter .mega-linter.yml configuration issues. Use when linters aren't running as expected or configuration seems wrong.
allowed-tools	Read Grep Glob
argument-hint	[config-file-path]
model	sonnet
metadata	{"internal":true}

Diagnose MegaLinter configuration. Read the .mega-linter.yml (or path provided in $ARGUMENTS) and check for:

1. Configuration hierarchy: Env vars override .mega-linter.yml, which overrides descriptor defaults. Both .mega-linter.yml and .megalinter.yml are recognized.
2. ENABLE/DISABLE conflicts: ENABLE_LINTERS/DISABLE_LINTERS take precedence over ENABLE/DISABLE (descriptor-level). You can't enable a linter if its descriptor is disabled.
3. Filter patterns: Validate FILTER_REGEX_INCLUDE/FILTER_REGEX_EXCLUDE regex syntax
4. Linter variable naming: Must be UPPERCASE with _ separator matching the generated name DESCRIPTOR_LINTERNAME (e.g., PYTHON_PYLINT_ARGUMENTS, not pylint_arguments)
5. Flavor compatibility: If using a flavor image, verify the enabled linters exist in that flavor by checking flavors/<flavor>/flavor.json
6. EXTENDS: If using remote config inheritance via HTTPS URLs, verify they're accessible
7. APPLY_FIXES: Check the fix mode is compatible with the CI system — auto-commit requires write access to the branch
8. Pre/Post commands: Validate PRE_COMMANDS and POST_COMMANDS syntax (each needs command and cwd fields, cwd is root or workspace)
9. Common mistakes:
   • Using lowercase linter names (must be UPPERCASE)
   • Missing _ separator in linter-specific vars
   • Setting VALIDATE_ALL_CODEBASE=true in CI (slow — usually want diff-only)
   • Forgetting {LINTER}_FILTER_REGEX_INCLUDE/EXCLUDE overrides global filters

Reference megalinter/config.py for the full resolution logic.